The field of the present invention relates to firearms. In particular, hammer spring assemblies for firearms are described herein that provide a varying lever arm for exerting a spring force on a hammer of a firearm.
A wide variety of hammer spring assemblies or arrangements are used for firearms of various types. Some of these are described in:
U.S. Pat. No. 287,229 entitled “Magazine gun” issued Oct. 23, 1883 to Bullard;
U.S. Pat. No. 3,377,731 entitled “Lever action trigger system” issued Apr. 16, 1968 to Lawrence;
U.S. Pat. No. 3,726,040 entitled “Gun trigger mechanism” issued Apr. 10, 1973 to Cranston;
U.S. Pat. No. 4,040,196 entitled “Rifle” issued Aug. 9, 1977 to Smith et al;
U.S. Pat. No. 4,128,957 entitled “Revolver-type handgun” issued Dec. 12, 1978 to Lee;
U.S. Pat. No. 4,391,057 entitled “Actuator system for the return of the trigger in double-action revolvers” issued Jul. 5, 1983 to Bornancini;
U.S. Pat. No. 4,908,970 entitled “Gun trigger” issued Mar. 20, 1990 to Bell;
U.S. Pat. No. 5,012,604 entitled “Trigger assembly” issued May 7, 1991 to Rogers;
U.S. Pat. No. 5,548,914 entitled “Gun trigger mechanism” issued Aug. 27, 1996 to Anderson;
U.S. Pat. No. 5,682,699 entitled “Single-shot falling block action rifle with improved safety” issued Nov. 4, 1997 to Gentry;
U.S. Pat. No. 7,181,880 entitled “Roller sear/hammer interface for firearms” issued Feb. 27, 2007 to Keeney;
U.S. Pat. No. 7,430,827 entitled “Gun trigger” issued Oct. 7, 2008 to Huber; and
U.S. Pat. No. 7,526,889 entitled “Trigger mechanism for handguns” issued May 5, 2009 to Metzger et al.
In the patents listed above, the hammer spring assembly exerts a spring force on the hammer at a fixed point on the hammer. Typically, the spring force is exerted by the spring or a spring-driven member at a pivot point fixed on the hammer or at a detent or depression on the hammer. In either case, the effective lever arm of the spring force on the hammer does not change as the hammer rotates. The user-applied torque required to cock the hammer against the spring force therefore typically increases (with increasing spring force as the spring is compressed) as the hammer rotates in a rearward direction as it is cocked.